error in slapd w/ example qmail-ldap defnition

[Daniel Canas M]

hello,

when I try to start the ldap-server on Suse 9.1, I get this error on  
startup.   "substr index of attribute "objectClass" disallowed"

it does not like the line :
index           objectclass eq,sub


Is it necessary for objectclass to be indexed by substring for  
qmailldap to work correctly?